U.S. patent application number 14/395460 was filed with the patent office on 2015-05-14 for roller position control in a toric-drive cvt.
The applicant listed for this patent is TRANSMISSION CVTCORP INC.. Invention is credited to Samuel Beaudoin, Kenneth Huston.
Application Number | 20150133262 14/395460 |
Document ID | / |
Family ID | 49382743 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150133262 |
Kind Code |
A1 |
Beaudoin; Samuel ; et
al. |
May 14, 2015 |
ROLLER POSITION CONTROL IN A TORIC-DRIVE CVT
Abstract
A roller position control mechanism including a steering
element, positioned inside the bearing of each roller and provided
with a skew shaft and a steering shaft defining an angle
therebetween. A spider element fixes the steering element to a
longitudinal shaft of the CVT and a control ring element
interconnects the steering elements of the various rollers.
Movement of the control ring element with respect to the spider
element translates to a tilting movement of the rollers, thanks to
the angle between the skew and steering shafts.
Inventors: |
Beaudoin; Samuel; (Quebec,
CA) ; Huston; Kenneth; (Montreal, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TRANSMISSION CVTCORP INC. |
Sainte-Julie |
|
CA |
|
|
Family ID: |
49382743 |
Appl. No.: |
14/395460 |
Filed: |
April 16, 2013 |
PCT Filed: |
April 16, 2013 |
PCT NO: |
PCT/CA2013/000366 |
371 Date: |
October 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61635381 |
Apr 19, 2012 |
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|
Current U.S.
Class: |
476/42 ;
476/46 |
Current CPC
Class: |
F16H 61/664 20130101;
F16H 2015/386 20130101; F16H 63/067 20130101; F16H 63/08 20130101;
F16H 15/38 20130101; F16H 63/3013 20130101 |
Class at
Publication: |
476/42 ;
476/46 |
International
Class: |
F16H 63/30 20060101
F16H063/30; F16H 15/38 20060101 F16H015/38; F16H 61/664 20060101
F16H061/664; F16H 63/08 20060101 F16H063/08 |
Claims
1. A roller position control mechanism for a CVT provided with a
longitudinal shaft, a first disk fixedly mounted to the
longitudinal shaft, rotating about a longitudinal axis and having a
toroidal surface; a second disk rotatably mounted to the
longitudinal shaft, rotating about the longitudinal axis and having
a toroidal surface facing the toroidal surface of the first disk;
and at least one roller in contact with both toroidal surfaces and
defining a roller plane perpendicular to a roller rotation axis,
the roller position control mechanism comprising: a spider element
rotatably mounted to the longitudinal shaft, the spider element
including, for each roller, a skew shaft generally parallel to the
longitudinal shaft; the skew shaft defining a skew axis passing
through the roller rotation axis; a steering element so mounted to
the skew shaft as to pivot about the skew axis; the steering
element including a steering shaft defining a steering axis
included in the roller plane; the steering axis defining an angle
with the skew axis while being on the same plane; each roller being
so pivotally mounted to the steering shaft as to pivot about the
steering axis; whereby, when the steering element is pivoted about
the skew axis, the roller pivots about the steering axis so that
the roller plane remains generally perpendicular to a radial plane
in which lies the skew axis, therefore dictating a tilt angle of
the roller with respect to the first and second disks.
2. A roller position control mechanism as recited in claim 1,
wherein the roller is mounted to the steering shaft via a bearing
holder, pivotally mounted to the steering shaft, and a bearing
provided between the bearing holder and the roller to allow the
roller to rotate about the roller rotation axis.
3. A roller position control mechanism as recited in claim 1,
further comprising a control ring interconnecting the steering
elements of each roller provided between the first and second
disks.
4. A roller position control mechanism as recited in claim 3,
wherein the steering element includes a control shaft defining a
control axis generally parallel to the longitudinal axis and spaced
apart from the skew shaft, the control shaft interconnecting the
steering element to the control ring so that a rotation of the
control ring about the longitudinal axis causes the steering
element to pivot about the skew axis and the roller to pivot about
the steering axis.
5. A roller position control mechanism as recited in claim 4,
wherein the steering element is generally spherical and includes a
projection to receive the control shaft.
6. A roller position control mechanism as recited in claim 1,
wherein the angle between the skew axis and the steering axis is
about 45 degrees.
7. A roller position control mechanism as recited in claim 1,
wherein the first disk is an input disk and wherein the second disk
is an output disk.
8. A CVT comprising: a longitudinal shaft; first and second disks
fixedly mounted to the longitudinal shaft, rotating about a
longitudinal axis and having respective first and second toroidal
surfaces; a third disk rotatably mounted to the longitudinal shaft,
rotating about a longitudinal axis and having first and second
toroidal surfaces respectively facing the first and second toroidal
surfaces of the first and second disks; at least one first roller
in contact with both first toroidal surfaces and defining a first
roller plane perpendicular to the roller rotation axis; at least
one second roller in contact with both second toroidal surfaces and
defining a second roller plane perpendicular to the roller rotation
axis; a roller position control mechanism comprising: a first
spider element rotatably mounted to the longitudinal shaft, the
first spider element including, for each first roller, a first skew
shaft generally parallel to the longitudinal shaft; the first skew
shaft defining a first skew axis passing through the first roller
rotation axis; a first steering element so mounted to the first
skew shaft as to pivot about the first skew axis; the first
steering element including a first steering shaft defining a first
steering axis included in the roller plane; the first steering axis
defining an angle with the first skew axis while being on the same
plane; each first roller being so pivotally mounted to the first
steering shaft as to pivot about the first steering axis; a first
control ring interconnecting the first steering elements of each
first roller so that they pivot about respective first skew shafts
simultaneously; a second spider element rotatably mounted to the
longitudinal shaft, the second spider element including, for each
second roller, a second skew shaft generally parallel to the
longitudinal shaft; the second skew shaft defining a second skew
axis passing through the second roller rotation axis; a second
steering element so mounted to the second skew shaft as to pivot
about the skew axis; the second steering element including a second
steering shaft defining a second steering axis included in the
roller plane; the second steering axis defining an angle with the
second skew axis while being on the same plane; each second roller
being so pivotally mounted to the second steering shaft as to pivot
about the second steering axis; a second control ring
interconnecting the second steering elements of each second roller
so that they pivot about respective second skew shafts
simultaneously; the first and second control rings being
interconnected to as to move the first and second steering elements
simultaneously; whereby, when the first and second steering
elements are pivoted about their respective first and second skew
shafts by their respective control ring, the first and second
rollers pivot about their respective first and second steering axis
so that the each of the first and second roller planes of the first
and second rollers remain generally perpendicular to a respective
radial plane in which lies their respective first and second skew
axis, therefore dictating a tilt angle or the first and second
rollers with respect to the first, second and third disks.
9. A CVT as recited in claim 8, wherein the first and second
control rings are respectively connected to the first and second
steering elements via first and second control shafts generally
parallel to the longitudinal shaft and respectively radially spaced
apart from the first and second skew shafts.
10. A CVT as recited in claim 8, wherein a) each of the first
rollers are mounted to the first steering shaft via a first bearing
holder, pivotally mounted to the first steering shaft, and a first
bearing provided between the first bearing holder and the first
roller to allow the first roller to rotate about the first roller
rotation axis; and b) each of the second rollers are mounted to the
second steering shaft via a second bearing holder, pivotally
mounted to the second steering shaft, and a second bearing provided
between the second bearing holder and the second roller to allow
the second roller to rotate about the second roller rotation
axis.
11. A CVT as recited in claim 8, wherein a) the first steering
element includes a first control shaft defining a first control
axis generally parallel to the longitudinal axis and spaced apart
from the first skew shaft, the first control shaft interconnecting
the first steering element to the first control ring so that a
rotation of the first control ring about the longitudinal axis
causes the first steering element to pivot about the first skew
axis and the first roller to pivot about the first steering axis,
and b) the second steering element includes a second control shaft
defining a second control axis generally parallel to the
longitudinal axis and spaced apart from the second skew shaft, the
second control shaft interconnecting the second steering element to
the second control ring so that a rotation of the second control
ring about the longitudinal axis causes the second steering element
to pivot about the second skew axis and the second roller to pivot
about the second steering axis.
12. A CVT as recited in claim 8, wherein the first and second
steering elements are generally spherical and include respective
first and second projections to respectively receive first and
second control shafts to respectively interconnect the first and
second steering elements to the first and second control rings.
13. A CVT as recited in claim 8, wherein the angle between the
first skew axis and the first steering axis is about 45 degrees,
and wherein the angle between the second skew axis and the second
steering axis is about 45 degrees.
14. A CVT as recited in claim 8, wherein the first and second disks
are input disks and wherein the third disk is an output disk.
15. A CVT comprising: a longitudinal shaft; a first disks fixedly
mounted to the longitudinal shaft, rotating about a longitudinal
axis and having a toroidal surface; a second disk rotatably mounted
to the longitudinal shaft, rotating about a longitudinal axis and
having a toroidal surface facing the toroidal surface of the first
disk; three rollers in contact with both toroidal surfaces and
defining a roller plane perpendicular to the roller rotation axis;
a roller position control mechanism comprising: a spider element
rotatably mounted to the longitudinal shaft, the spider element
including, for each roller, a skew shaft generally parallel to the
longitudinal shaft; the skew shaft defining a skew axis passing
through the roller rotation axis; for each roller, a steering
element so mounted to the skew shaft as to pivot about the skew
axis; the steering element including a steering shaft defining a
steering axis included in the roller plane; the steering axis
defining an angle with the skew axis while being on the same plane;
each roller being so pivotally mounted to the steering shaft as to
pivot about the steering axis; a control ring interconnecting the
steering elements of each roller so that they pivot about
respective skew shafts simultaneously; whereby, when the steering
elements are pivoted about their respective skew shafts by the
control ring, the three rollers pivot about their respective
steering axis so that each roller plane remain generally
perpendicular to a respective radial plane passing through the
respective skew axis, therefore dictating a tilt angle of the
rollers with respect to the first and second disks.
16. A CVT as recited in claim 15, wherein the control ring is
connected to the steering element via a control shaft generally
parallel to the longitudinal shaft and radially spaced apart from
the skew shaft.
17. A CVT as recited in claim 15, wherein each roller is mounted to
the steering shaft via a bearing holder, pivotally mounted to the
steering shaft, and a bearing provided between the bearing holder
and the roller to allow the roller to rotate about the roller
rotation axis.
18. A CVT as recited in claim 16, wherein the steering element
includes a control shaft defining a control axis generally parallel
to the longitudinal axis and spaced apart from the skew shaft, the
control shaft interconnecting the steering element to the control
ring so that a rotation of the control ring about the longitudinal
axis causes the steering element to pivot about the skew axis and
the roller to pivot about the steering axis.
19. A CVT as recited in claim 18 wherein the steering element is
generally spherical and include a projection to receive the control
shaft.
20. A CVT as recited in any claim 15, wherein the angle between the
skew axis and the steering axis is about 45 degrees.
21. A CVT as recited in claim 15, wherein the first disk is an
input disk and wherein the second disk is an output disk.
Description
FIELD
[0001] The present invention generally relates to Toric-drive
Continuously Variable Transmissions. More specifically, the present
invention is concerned with the control of the roller position in a
Toric-drive CVT.
BACKGROUND
[0002] Toric-drive Continuously Variable Transmissions (hereinafter
generically referred to as "CVT") are believed known in the art.
The operation of such a CVT will therefore only be briefly
discussed herein.
[0003] Generally stated, a CVT is provided with a drive disk having
a toroidal surface, a driven disk also having a toroidal surface
and facing the toroidal surface of the drive disk, both disks being
linked by rollers in contact with their respective toroidal
surfaces. The tilt angle of the rollers with respect to the drive
and driven disks dictates the speed ratio between the driven and
drive disks since this angle dictates the radial position at which
the rollers contact the two toroidal surfaces.
[0004] These rollers are generally linked to one another so that
their tilt angle is the same. A roller position control mechanism
is therefore required to insure that the rollers present the same
tilt angle and move simultaneously when they change from one ratio
to another.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] In the appended drawings:
[0006] FIG. 1 is a schematic perspective view of a dual cavity full
toroidal CVT provided with a roller position control mechanism
according to an illustrative embodiment;
[0007] FIG. 2 is an exploded view of a roller provided with roller
position control elements;
[0008] FIG. 3 is a sectional view of a roller shown in a unitary
ratio; the section being taken in a radial plane in which lies the
skew shaft and the longitudinal axis of the CVT;
[0009] FIG. 4 is a sectional view taken along line 4-4 of FIG.
3;
[0010] FIG. 5 is a sectional view taken along line 5-5 of FIG.
3;
[0011] FIG. 6 is a sectional view similar to FIG. 3 but showing the
roller in a maximal overdrive position;
[0012] FIG. 7 is a sectional view taken along line 7-7 of FIG.
6;
[0013] FIG. 8 is a sectional view taken along line 8-8 of FIG.
6;
[0014] FIG. 9 is a sectional view similar to FIG. 3 but showing the
roller in a maximal underdrive position;
[0015] FIG. 10 is a sectional view taken along line 10-10 of FIG.
9; and
[0016] FIG. 11 is a sectional view taken along line 11-11 of FIG.
9.
DETAILED DESCRIPTION
[0017] An object is generally to provide an improved roller
position control in a toric-drive CVT.
[0018] According to an illustrative embodiment, there is provided a
* A roller position control mechanism for a CVT provided with a
longitudinal shaft, a first disk fixedly mounted to the
longitudinal shaft, rotating about a longitudinal axis and having a
toroidal surface; a second disk rotatably mounted to the
longitudinal shaft, rotating about the longitudinal axis and having
a toroidal surface facing the toroidal surface of the first disk;
and at least one roller in contact with both toroidal surfaces and
defining a roller plane perpendicular to a roller rotation axis,
the roller position control mechanism comprising:
[0019] a spider element rotatably mounted to the longitudinal
shaft, the spider element including, for each roller, a skew shaft
generally parallel to the longitudinal shaft; the skew shaft
defining a skew axis passing through the roller rotation axis;
[0020] a steering element so mounted to the skew shaft as to pivot
about the skew axis; the steering element including a steering
shaft defining a steering axis included in the roller plane; the
steering axis defining an angle with the skew axis while being on
the same plane; each roller being so pivotally mounted to the
steering shaft as to pivot about the steering axis;
[0021] whereby, when the steering element is pivoted about the skew
axis, the roller pivots about the steering axis so that the roller
plane remains generally perpendicular to a radial plane in which
lies the skew axis, therefore dictating a tilt angle of the roller
with respect to the first and second disks.
[0022] According to another illustrative aspect, there is provided
a A CVT comprising:
[0023] a longitudinal shaft;
[0024] first and second disks fixedly mounted to the longitudinal
shaft, rotating about a longitudinal axis and having respective
first and second toroidal surfaces;
[0025] a third disk rotatably mounted to the longitudinal shaft,
rotating about a longitudinal axis and having first and second
toroidal surfaces respectively facing the first and second toroidal
surfaces of the first and second disks;
[0026] at least one first roller in contact with both first
toroidal surfaces and defining a first roller plane perpendicular
to the roller rotation axis;
[0027] at least one second roller in contact with both second
toroidal surfaces and defining a second roller plane perpendicular
to the roller rotation axis;
[0028] a roller position control mechanism comprising:
[0029] a first spider element rotatably mounted to the longitudinal
shaft, the first spider element including, for each first roller, a
first skew shaft generally parallel to the longitudinal shaft; the
first skew shaft defining a first skew axis passing through the
first roller rotation axis;
[0030] a first steering element so mounted to the first skew shaft
as to pivot about the first skew axis; the first steering element
including a first steering shaft defining a first steering axis
included in the roller plane; the first steering axis defining an
angle with the first skew axis while being on the same plane; each
first roller being so pivotally mounted to the first steering shaft
as to pivot about the first steering axis;
[0031] a first control ring interconnecting the first steering
elements of each first roller so that they pivot about respective
first skew shafts simultaneously;
[0032] a second spider element rotatably mounted to the
longitudinal shaft, the second spider element including, for each
second roller, a second skew shaft generally parallel to the
longitudinal shaft; the second skew shaft defining a second skew
axis passing through the second roller rotation axis;
[0033] a second steering element so mounted to the second skew
shaft as to pivot about the skew axis; the second steering element
including a second steering shaft defining a second steering axis
included in the roller plane; the second steering axis defining an
angle with the second skew axis while being on the same plane; each
second roller being so pivotally mounted to the second steering
shaft as to pivot about the second steering axis;
[0034] a second control ring interconnecting the second steering
elements of each second roller so that they pivot about respective
second skew shafts simultaneously; the first and second control
rings being interconnected to as to move the first and second
steering elements simultaneously;
[0035] whereby, when the first and second steering elements are
pivoted about their respective first and second skew shafts by
their respective control ring, the first and second rollers pivot
about their respective first and second steering axis so that the
each of the first and second roller planes of the first and second
rollers remain generally perpendicular to a respective radial plane
in which lies their respective first and second skew axis,
therefore dictating a tilt angle or the first and second rollers
with respect to the first, second and third disks.
[0036] According to a third aspect, there is provided a A CVT
comprising:
[0037] a longitudinal shaft;
[0038] a first disks fixedly mounted to the longitudinal shaft,
rotating about a longitudinal axis and having a toroidal
surface;
[0039] a second disk rotatably mounted to the longitudinal shaft,
rotating about a longitudinal axis and having a toroidal surface
facing the toroidal surface of the first disk;
[0040] three rollers in contact with both toroidal surfaces and
defining a roller plane perpendicular to the roller rotation
axis;
[0041] a roller position control mechanism comprising:
[0042] a spider element rotatably mounted to the longitudinal
shaft, the spider element including, for each roller, a skew shaft
generally parallel to the longitudinal shaft; the skew shaft
defining a skew axis passing through the roller rotation axis;
[0043] for each roller, a steering element so mounted to the skew
shaft as to pivot about the skew axis; the steering element
including a steering shaft defining a steering axis included in the
roller plane; the steering axis defining an angle with the skew
axis while being on the same plane; each roller being so pivotally
mounted to the steering shaft as to pivot about the steering
axis;
[0044] a control ring interconnecting the steering elements of each
roller so that they pivot about respective skew shafts
simultaneously;
[0045] whereby, when the steering elements are pivoted about their
respective skew shafts by the control ring, the three rollers pivot
about their respective steering axis so that each roller plane
remain generally perpendicular to a respective radial plane passing
through the respective skew axis, therefore dictating a tilt angle
of the rollers with respect to the first and second disks.
[0046] The use of the word "a" or "an" when used in conjunction
with the term "comprising" in the claims and/or the specification
may mean "one", but it is also consistent with the meaning of "one
or more", "at least one", and "one or more than one". Similarly,
the word "another" may mean at least a second or more.
[0047] As used in this specification and claim(s), the words
"comprising" (and any form of comprising, such as "comprise" and
"comprises"), "having" (and any form of having, such as "have" and
"has"), "including" (and any form of including, such as "include"
and "includes") or "containing" (and any form of containing, such
as "contain" and "contains"), are inclusive or open-ended and do
not exclude additional, unrecited elements or process steps.
[0048] The term "about" is used to indicate that a value includes
an inherent variation of error for the device or the method being
employed to determine the value.
[0049] It is to be noted that while the expression "CVT", standing
for Continuously Variable Transmission is used herein to refer to a
dual-cavity full toroidal CVT, however this expression is to be
construed herein and in the appended claims as any type of toroidal
CVT such as, for example, half-toroidal CVT and single cavity
toroidal CVT.
[0050] It is to be noted that the expression "overdrive" when used
herein in the context of a CVT, is to be construed herein and in
the appended claims as a condition where the CVT ratio is such that
the CVT output speed is higher than the CVT input speed.
[0051] It is to be noted that the expression "underdrive" when used
herein in the context of a CVT, is to be construed herein and in
the appended claims as a condition where the CVT ratio is such that
the CVT output speed is lower than the CVT input speed.
[0052] Other objects, advantages and features of the roller
position control mechanism will become more apparent upon reading
of the following non-restrictive description of illustrative
embodiments thereof, given by way of example only with reference to
the accompanying drawings.
[0053] Generally stated, the roller position control mechanism as
described in an illustrative embodiment includes a steering
element, positioned inside the bearing of each roller and provided
with a skew shaft and a steering shaft defining an angle
therebetween. A spider element fixes the steering element to a
longitudinal shaft of the CVT and a control ring element
interconnects the steering elements of the various rollers.
Movement of the control ring element translates to a tilting
movement of the rollers, thanks to the angle between the skew and
steering shafts.
[0054] Turning now to the appended figures, a CVT 20 provided with
a roller position control mechanism 22 will be described.
[0055] The toric-drive CVT 20 includes a longitudinal main shaft 24
to which are fixedly mounted first and second drive disks 26 and 28
for rotation therewith about a longitudinal axis 30. A driven disk
32 is rotatably mounted to the main shaft 24, for example via
bearings (see 33 in FIG. 3). Three rollers 34 are provided between
the first drive disk 26 and the driven disk 32 while three rollers
36 are provided between the second drive disk 28 and the driven
disk 32. The main shaft 24 is mounted to a casing (not shown) via
bearings (also not shown).
[0056] The first drive disk 26 and the driven disk 32 include
respective facing toroidal surfaces 27 (only one visible in FIG. 1)
defining a first cavity while the second drive disk 28 and the
driven disk 32 include respective facing toroidal surfaces 33 (only
one visible in FIG. 1) defining a second cavity.
[0057] It will easily be understood by one skilled in the art that
the dual cavity toric-drive CVT 20 is only schematically
illustrated in FIG. 1. Indeed, many subsystems such as, for
example, a casing and various sub-assemblies, are not shown for
clarity and since they have no incidence on the structure and
operation of the roller position control mechanism described
herein.
[0058] The roller position control mechanism 22 includes, for each
cavity, a spider element 38, a control ring 40 and three roller
mounting mechanisms 42, better seen in exploded FIG. 2.
[0059] From FIG. 2, the roller mounting mechanism 42 includes a
steering element 44 mounted to an end 46 of the spider element 38
via a skew shaft 48 so as to allow the steering element 44 to pivot
about a skew axis 50, which is parallel to the longitudinal axis 30
of the CVT 20.
[0060] The steering element 44 includes a steering shaft in the
form of two steering pins 52 so interconnecting the steering
element 44 to a bearing holder 54 that the bearing holder 54 can
pivot about the steering axis 56.
[0061] A bearing assembly 58 is used to rotatably mount the roller
34 to the bearing holder 54.
[0062] As can be seen from this Figure, the skew axis 50 and the
steering axis 56 define an angle while being in the same plane.
Furthermore, the skew axis 50 and the steering axis 56 pass through
the rotation axis 60 of the roller 34 while the steering axis 56 is
generally contained in the plane defined by the roller 34 when
assembled.
[0063] The steering element 44 includes an aperture 62 to receive
the skew shaft 48 and two apertures 64 (only one shown) to receive
the steering pins 52. The steering element 44 also includes a
projection 66 provided with an aperture 68 configured to receive a
control shaft 70 linking the steering element 44 to the control
ring 40. The control shaft 70 being parallel to the skew shaft 48.
The control ring 40 is so mounted to the main shaft 24 that it can
pivot about the longitudinal axis 30 when actuated by an
appropriate actuator (not shown).
[0064] One skilled in the art will understand that all the elements
of the roller mounting mechanism 42 of FIG. 2 are present for each
of the three rollers 34 of the first cavity.
[0065] Similarly, all the elements of FIG. 2, including the spider
38, are also present in the second cavity. One skilled in the art
will understand that since the first and second cavities share a
disk 32, the various parts of the roller position control of the
second cavity are mirror images of their counterpart of the first
cavity with reference to the disk 32.
[0066] Since the steering element 44 of each roller of both
cavities are interconnected by control rings 40, movements of the
steering elements 44 are done simultaneously and of the same skew
angle by a pivot action of the control rings 40 about the
longitudinal axis.
[0067] Turning now to FIGS. 3 to 5 of the appended drawings,
showing a roller 34 in a unitary ratio, i.e. that the rotational
speed of the output disk 32 is the same as the rotational speed in
the input disk 26.
[0068] FIG. 3 is a sectional view taken along a radial plane in
which lies the skew axis 50 of the skew shaft 48 and the
longitudinal axis 30 of the CVT. As can be seen from this figure,
the control ring 40 is mounted to a control hub 72 linking the
control rings 40 of both cavities. The control hub 72 is so
rotatably mounted to the main shaft 24 and so as to be in a
position to pivot when appropriately actuated by an actuator (not
shown).
[0069] The spider element 38 is so mounted to a spider hub 74
rotatably mounted to the control hub 72 as to allow pivotment of
the control hub 72. The spider hub 74 is also mounted to a casing
(not shown) of the CVT 20 so that rotation of the spider hub 74
about the longitudinal axis 30 is prevented.
[0070] As can be seen from FIG. 3, which illustrates the CVT 20 in
a steady state, i.e. when the control ring 40 has been immobilized
for a predetermined time, the plane 75 defined by the roller 34 is
generally perpendicular to a radial plane in which lies the skew
axis of the skew shaft 48 and the longitudinal axis 30 of the CVT,
i.e. the plane in which FIG. 3 is taken.
[0071] FIG. 4 illustrates that the control shaft 70 is linked to
the control ring 40 via a radial slot 76, thereby allowing a pivot
movement of the control ring 40 with respect to the rotationally
fixed spider 38.
[0072] FIGS. 6 to 8 are views similar to FIGS. 3 to 5 but
illustrate the roller 34 in a maximal overdrive ratio, when in a
steady state.
[0073] As can be seen from FIG. 7, the change from the unity ratio
of FIGS. 3 to 6 to the maximal overdrive ratio has been initiated
by a pivot action of the control ring 40 (see arrow 78). This pivot
action moves the control element 44 about the shaft 48, to thereby
change the angle between the steering shaft and the main shaft 24.
Accordingly, this pivot action initially results in the plane 75 of
the roller no longer being generally perpendicular to the radial
plane on which lie the longitudinal axis of the CVT 30 and the
roller skew axis 50. Accordingly each roller is no longer rolling
along a steady state circular track along the disks 26 and 32 but
on a transitory spiral track forcing the roller 34 contact between
the input disk 26 to move on a higher track while bringing the
contact of the roller 34 and the output disk 32 to a lower track.
The various forces generated by the counter-rotating disks 26 and
32 are such that this tilting movement of the roller 34 pivots the
bearing holder 54 about the steering axis 56 to thereby bring the
roller 34 in a position where its plane is generally perpendicular
to a radial plane where lie the skew axis of the skew shaft 48.
This situation is shown in FIGS. 6 to 8 representing the roller 34
when it reaches steady state thus rolling back on a circular track
along the disks 26 and 32 but now at the maximum overdrive ratio of
the CVT.
[0074] FIGS. 9 to 11 are views similar to FIGS. 3 to 5 but
illustrate the roller 34 in a maximal underdrive ratio, when in a
steady state.
[0075] As can be seen from FIG. 10, the change from the unity ratio
of FIGS. 3 to 6 to the maximal underdrive ratio has been initiated
by a pivot action of the control ring 40 (see arrow 80). This pivot
action moves the control element 44 about the shaft 48, to thereby
change the angle between the steering shaft and the main shaft 24.
Accordingly, this pivot action initially results in the roller
plane no longer being generally perpendicular to the radial plane
on which lie the longitudinal axis of the CVT 30 and the roller
skew axis 50. Accordingly each roller is no longer rolling along a
steady state circular track along the disks 26 and 32 but on a
transitory spiral track forcing the roller 34 contact between the
input disk 26 to move on a lower track while bringing the contact
of the roller 34 and the output disk 32 to a higher track. The
various forces generated by the counter-rotating disks 26 and 32
are such that this tilting movement of the roller 34 pivots the
bearing holder 54 about the steering axis 56 to thereby bring the
roller 34 in a position where its plane is generally perpendicular
to a radial plane where lie the skew axis of the skew shaft 48 and
the longitudinal axis 30. This situation is shown in FIGS. 9 to 11
representing the roller 34 when it reaches steady state thus
rolling back on a circular track along the disks 26 and 32 but now
at the maximum underdrive ratio of the CVT.
[0076] It will be apparent to one skilled in the art that the
transmission ratio of the CVT 20 can be anywhere between the
overdrive ratio of FIGS. 6 to 8 and the underdrive ratio of FIGS. 9
to 11.
[0077] One skilled in the art will understand that the angle
present between the skew axis and the steering axis, the geometry
of the rollers and of the toroidal surfaces of the input and output
disks, along with the various forces imposed on the rollers by the
counter rotating input and output disks, are such that, when the
CVT is in a steady state, the plane of each roller is generally
perpendicular to a radial plane in which lie the longitudinal axis
of the CVT shaft and the skew axis of the skew shaft of that
particular roller, which brings stability to the roller and to the
CVT as a whole.
[0078] It will be understood by one skilled in the art that the
angle defined by the skew axis 50 and the steering axis 56 is
highly dependent on the geometry and size of the various elements
of the CVT and on the maximal desired tilt angle of the rollers. In
the illustrative example shown in the drawings and described
herein, it has been found that an angle of about 45 degrees between
the axes is interesting. It will be understood that by decreasing
this angle, the pivoting movement of the control ring 40 required
to move the rollers to the maximal tilt angle needs to be greater
which may cause clearance problems. On the other hand, if the angle
defined by the skew axis 50 and the steering axis 56 is greater,
the range of pivoting of the control ring 40 to move between the
maximal tilt angles of the rollers is decreased which may magnify
the effects of any deviation from manufacturing tolerances.
[0079] One skilled in the art will understand that while the
steering element 44 is shown as a generally spherical element, that
this shape could be changed should more space be available in the
bearing holder 54. In other words, the generally spherical shape of
the steering element 44 is for space saving purpose and not for
functionality.
[0080] In the illustrative embodiment described hereinabove and
shown in the appended drawings, the pivot movement of the control
ring 40 is the cause of the change of the rollers tilt angle. One
skilled in the art will understand that the cause is really the
modification of the pivotal position of the control ring with
respect to the spider element 38 that is rotationally fixed.
Accordingly, it would be possible to design a roller position
control mechanism where the control ring would be fixed and where
the spider element could pivot.
[0081] One skilled in the art will understand that while a
double-cavity toroidal CVT has been illustrated herein, other
toroidal CVT technologies could be used. As non-limiting examples,
single cavity toroidal CVTs and half-toroidal CVTs could be
used.
[0082] It is to be understood that the roller position control is
not limited in its application to the details of construction and
parts illustrated in the accompanying drawings and described
hereinabove. The roller position control is capable of other
embodiments and of being practiced in various ways. It is also to
be understood that the phraseology or terminology used herein is
for the purpose of description and not limitation. Hence, although
the roller position control has been described hereinabove by way
of illustrative embodiments thereof, it can be modified, without
departing from the spirit, scope and nature of the subject
invention.
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